Theoretical and experimental psychoacoustic research oriented toward the creation of a coherent, quantitative, and unified theory of intensity perception and loudness is proposed. This research is a continuation of previous research by the same investigators and involves the development and/or integration of models of decision-making, sensory processing, short-term memory, and perceptual-context effects; experiments on discrimination and identification of sound intensity and on loudness comparisons between different types of stimuli; analyses of data processing procedures for estimation of parameters and for choosing between alternative theories; and application of the models and experimental technques to the study of intensity perception and loudness in impaired listeners.